The principle of operation of the device for adjusting a discharge gap of an inertia cone crusher is based on conversion of the angle of deflection of the crusher breaking head axis from the vertical into an electrical signal proportional to the size of the discharge gap.
Known in the art is a device for adjusting the discharge gap of an inertia cone crusher (cf. USSR Author's Certificate No. 196,536), wherein the angle sensor responsive to deflection of the breaking head axis from the vertical comprises a spring-loaded rod enclosed in a cylindrical casing and having its one end provided with a roller co-operating with the breaking head, and a rheostat-like sensitive member linked with the other end of the rod. The sensor follows up the angle of deflection of the breaking head axis from the vertical through the roller pressed against the breaking head. As soon as the angle departs from the value corresponding to the optimal crushing conditions, the sensitive member responding to the variation of the rod position sends a signal to an electric measuring unit which, in turn, generates a signal for an actuator to lift or to lower the crushing bowl and hence to change the size of the discharge gap.
The device described hereinabove is of a low reliability and has insufficient adjustment accuracy because of gradual wear of the roller moving along the breaking head surface.
Also known in the art is a device for adjusting the discharge gap of an inertia cone crusher (cf. USSR Author's Certificate No. 458,335), that comprises an angle sensor responsive to deflection of the breaking head axis from the vertical, a control and measuring means used to process and to analyze the sensor signals and to generate a control signal according to the results of this analysis, and an actuator employed to vertically displace the crushing bowl of the crusher for changing the size of the discharge gap. The breaking head is fastened to a shaft coupled mechanically with an out-of-balance weight rotated with respect to the vertical axis of the crusher by a drive with a ball spindle having a ferromagnetic coating or made completely of a ferromagnetic material.
The control and measuring means of the device comprises a signal preprocessing unit connected to the sensor output, a discharge gap setter and a comparison unit having its inputs connected to the output of the signal preprocessing unit and to the output of the discharge gap setter respectively. The actuator is electrically coupled with the output of the comparison unit.
In the device being described, the angle sensor responsive to deflection of the breaking head axis from the vertical is an inductive sensor including core-mounted inductance coils, evenly spaced, around the ball spindle in an annular holder, with the annular holder being attached to the housing of the bearing wherein the lower head of the ball spindle is installed. Every pair of inductance coils arranged oppositely are hooked into two adjacent arms of the semibridge circuit operated from a sine-wave voltage generator.
As the ball spindle rotates, the out-of-balance weight produces a centrifugal force deviating the shaft with the breaking head, mounted thereon from the vertical. The shaft drives the upper head of the ball spindle which performs a circular swinging motion, whereby the spindle approaches and moves away from the inductance coils, thus causing a variation in inductance of the coils. The transducer generates a signal depending, with the given parameters of the inductance coils, upon the size of the air gap between the core edges of these coils and the ball spindle, i.e. upon the angle of deflection of the ball spindle and, hence, upon the angle of deflection of the breaking head axis from the vertical, and said angles representing the size of the discharge gap.
A disadvantage of such prior art device is that it is difficult to compensate for the initial output voltage of the inductive sensor, increasing the control error. Furthermore, the inductive sensor is inefficient when large air gaps (over 20 mm) are set between the inductance coils and the ball spindle. It is a feature of the inductive sensor that its output signal is sharply reduced as the distance between the inductance coils and the co-operating members, that is, in this particular case the ball spindle increases, and whenever said distance is over 20 mm, the transducer signal is so weak that it is commensurable with the noise level. As a result the adjustment accuracy is insufficient. The described prior art device is, therefore, applicable only to small-size crushers with a breaking head base of not over 600 mm in diameter and with a discharge gap size of not over 30 mm. The design of such crushers enables arrangement of the inductance coils at a distance not exceeding 20 mm from the ball spindle. In large-size crushers with a diameter of the breaking head base of, say, 1750 to 2000 mm, the discharge gap can be as large as 100 mm, which corresponds to relatively large angular deflections of the breaking head axis from the vertical. The coils of the sensor in such a crusher are disposed at a greater distance from the ball spindle.
Moreover, the use of the device under consideration is restricted only to small-size crushers because the inductance coils of the sensor are arranged around the ball spindle at the level of the lower head thereof. In large-size crushers, such a mutual arrangement of the transducer and of the ball spindle hampers the installation and dismantling of the sensor since the mass of the ball spindle and of the out-of-balance weight is rather large, whereby the sensor can be damaged by the ball spindle as a result of its upset in the course of assembling and disassembling the sensor. Special means are, therefore, required to protect the sensor, that complicate the device construction.